US2575989A - Treatment of petroleum distillates - Google Patents

Description

Patented Nov. 20, 1951 TREATMENT OF PETROLEUM DISTILLATES Erving Arundale, Westfield, and John P. Thorn,

Cranford, N. J assignors to Standard Oil Development Company, a corporation of Delaware Application September 3, 1949, Serial No. 113,942

12 Claims. 1

The present invention is concerned with an improved process for the production of high quality petroleum products. The invention is more particularly concerned with the production of high quality petroleum products boiling below about 700 F. especially those products which boil in the motorfuel boiling range. In accordance with the present process objectionable sulfur compounds, as for example mercaptans, are removed. from petroleum distillates containing the same or are converted to relatively innocuous compounds by treating the distillates with an alkylene oxide in the presence of an alkaline catalyst.

In the production of high quality petroleum products, as for example in the production of petroleum products boiling in the motor fuel boiling range, it is known to use various procedures either to remove mercaptans from the oil or to convert these mercaptans to less objectionable sulfur compounds. A few of the conversion processes comprise copper sweetening, Doctor treatment, hypochlorite sweetening, air sweetening and the like. Processes which remove mercaptans or reduce thesulfur content of the oil comprise caustic treatment and treatment with sulfuric acid. While these processes are in general satisfactory, they all have certain limitations which to some extent control their utilization. For example in the copper and Doctor sweetening processes the treating agent must be regenerated for economical operation and, in certain instances, objectionable emulsions are formed. The hypochlorite and air sweetening processes can be applied to cracked distillates but the products usually contain high gum contents. Acid treating is an efiective means for reducing the sulfur content of petroleum fractions but, in the case of cracked gasolines, high polymer losses and a reduction in octane number are experienced. Finally treatment with aqueous caustic solutions alone i not entirely satisfactory since the higher mercaptans are not removed in such a process. To present process employing an alkylene oxide in the presence of an alkaline catalyst produces a satisfactory sweetened product in an efficient and economical operation.

The present invention may be understood by reference to the drawing illustrating one embodiment of the same. An oil feed stream, which for the purpose of illustration is assumed to comprise a naphtha boiling in the range from about 80 F. to 450 F. and containing mercaptans,

is introduced into the system by means of feed line I. A caustic solution, which for the purpose of illustration is assumed to be an aqueous solutioncontaining 15% sodium hydroxide by weight, is added to the oil in line I by means of line 2. The respective streams are mixed in orifice mixer or equivalent means 3. The stream is then in troduced into settling zone 4 wherein a caustic phase and an oil phase form. The lower caustic phase can be removed by means of line 5 and regenerated or recycled to line 2 via line l3. The treated oil phase isremoved by means of line 6 and mixed with additional sodium hydroxide solution which is introduced by means of line 1.

Although the concentration of the caustic solution may vary appreciably it is assumed that a 15% by weight caustic soda solution is employed.

In accordance with the present invention an alkylene oxide, as for example ethylene oxide, is then introduced by means of line 8 and the respective streams are thoroughly mixed by passing through an orifice mixer or equivalent mixing device 9. The stream is introduced into settling Zone l0 wherein an oil phase and a spent caustic phase separate. The upper oil phase free of mercaptans is removed from settler ID by means of line H and further refined as desired. This stream is preferably water washed and may in some instances be rerun, although this latter operation is only necessary if maximum sulfur reduction is desired. The caustic phase is withdrawn from the bottom of zone H) by means of line l2 and may be Withdrawn from the system. However, in general, it is preferred to recycle this stream and introduce it into the oil feed stream by means of line l3 or line 1.

Sour virgin or cracked hydrocarbon distillates can be treated in this manner and the process of the present invention secures advantage over acid treating in that; (a) the products do not require rerunning; (b) there is no poly mer loss in the case of cracked distillates and; (c) the octane number is not degraded.

The treating agent of the present invention comprises the use of an alkylene oxide in the presence of an alkaline catalyst. In general the alkylene oxide has the formula wherein R1, R2, R3, and R4 represent hydrogen atoms or alkyl groups containing from 1 to 2 carbon atoms. Satisfactory oxides are for example, ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, trimethylethylene oxide, and the like. The preferred treating agent comprises ethylene oxide (CH2OCH2).

The alkaline catalyst preferably comprises an alkali metal hydroxide solution, as for example,

a sodium hydroxide solution. Other alkaline catalysts which may be used, are potassium hydroxide, ammonium hydroxide, sodium carbonate or sodium bicarbonate.

The concentration of the respective treating" agents employed will vary appreciably depending upon the character of the oilbeing treated, as

well as, upon the character and concentration of the mercaptan constituents present. In general, it is preferred to employ from 0.05 to 5% by weight of the alkylene oxide based upon the weight of the oil being treated. The concentration will vary with the copper number and boiling range of the feed stock and the treating temperature, but will preferably be in the range from about 0.2 to. 0.8 weight percent. The amount of aqueous alkaline catalyst employed is preferably in the range from 5 to by volume based upon the volume of the oil being contacted but may vary from 1 to by volume. The concentration of the aqueous alkali solution is preferably in the range from 5% to 20% by Weight of alkali hydroxide based upon the total weight of the aqueous alkali solution although concentrations as high as 50% or as low as 1% can be employed.

The temperatures employed, as well as the pressure, may be varied appreciably. However, in general it is preferred that the temperature be below about 212 F. preferably in the range from 70 to 140 F. The timeo'f treatment may vary considerably depending on other operat-"- ing conditions. In general the time of contact varies from about 2 to 15 minutes. The process of the present invention may be more fully understood by the following examples illustrating embodiments of the same:

EXAMPLE 1 346 grams (500 cc.) of virgin naphtha of copper number 1 were placed in a one-quart pressure bottle. 50 cc. of a 5% sodium hydroxide solution and 3.4 grams of ethylene oxide were added and the batch shaken at room temperature for hour. The caustic layer was separated and the naphtha layer water washed twice with .50 cecrwater. The water was removed and the product filtered. This treated product had a copper number 01? one.

1 Milligrams of mercaptan sulfur per cc.

EXAMPLE 2 Additional operations were conducted in which the caustic solution concentration, quantity of. causticsolution, and amount and type of alkylene oxide were varied. The feed stocks comprised a sour virgin naphtha and a sour thermally cracked gasoline. Prior to contacting these 'n'ap'hthas with the a'lkylene oxide-caustic solution, theywere washed in an initial stage with 10 volume percent of 5% sodium hydroxide solution and then withlO vo1ume percent of waterin order to remove'h'ydrogen sulfide and caustic soluble mer'-' captans and thereby decrease the amount of alkylene oxide required. 500 cc. of the caustic washed hydrocarbon distillate were shakenat room temperature (unless otherwise specified) for 15 minutes with a'caustic soda solution both in the presenceand absence of small amounts ofethylene, propylene and isobutylene oxides. The batch was then allowed to settle, thecaustic layer was removed, and the hydrocarbon layer washed with '20 'voluine'percent' of waterbefore the copper number was determined thereon; The results of "these operations are. as "follows:

Allc'ylene oacz'd-e swecteninooj petroleum distillates SO-UR VIRGIN NAPHDHA 1 per cent 40 wt. per cent 15 wt. per cent 15 wt. per cent 15 Wt. percent 15 wt. per "cent 15 wt.

. per cent 15 wt. per cent 15 wt. per-cent 15 wt.

' per cent '5 wt; per cent caustic 2 alone per cent 10 wt. percent caustic 9 alone percent 15 wt. percent caustic 1 alone. per cent-25 wt. per cent'caustic 1 alone. per cent 40 wt. per cent caustic al0ne W .per cent 5 wt. per-cent caustic+0.8 wt. per cent ethylene oxide per cent 10 wt. per cent caustic+0.8 wtxperccnt ethy lenc oxide per cent 15 wt. per cent caustic-{-03 wt. per cent zawt. per cent cl'ai1stic+0.8 wt...

percentcaustic {-0.8 wt.

per cent 'ciustidi-OJ wt; V 'p'ercentcaustic+0.4 wt. per cent ethylene oxide per cent caustic+06 wt. per cent-ethylene'oxide per cent caustie+02wt per cent propyiene oxide. per cent'caustic +0.4 wt. per centpropylene oxide. per cent caustic+0.6 wtj'per cent propylene oxide. per cent caustic l0.2 wt. per'cent isobutylene oxid per cehtcaustic-l-OA wt. per cent isobutylene oxid percent 15 wt. per cent caustic+0.6 wt. per cent iscbutylei'ie-oxide 5 Vol. per cent mm. per cent caustic+0.2 wt. per cent ethylene oxide. 5 Vol. percent l5 w't. per centca'usticfi-OA wtper cent ethylene oxide- 5 Vol. per cent 15 wt. per cent caustic+0.6 wt. per cent ethylene oxida 20 Vol. percent 15 wt. per 'cent caustic+0.2 wt. per cent ethylen'eoxide 20 Vol. percent 15 wt. per cent caustic-H14 Wt. per cent ethylene oxide 20 Vol. per cent 15 wt. per cent caustic-F06 Wt.-p'cr centethylene oxide... 10 V01. per cent-l5 wt. per cent caustic+0.2 wt per cent ethylene oxide-(1'31 10 Vol. per cent 15 wt. per cent caustic-+0.4 wt. percent ethylene oxide (131; 7

10 V01. per cent 15 wt. per cent caustic+0.6 Wt. percent ethyleneo'xi ie*(l31 -F. e r

1 Coppcr number of untreated stock=50, after initialpaustic washing iii. Brominenumher 1.7, cgJg-risp: gray. 0.675; 1 Caustic means aqueous sodium hydroxide solution. J

Alkylene oxide sweetening of petroleum distillates Continued soon THERMALLY oaxoxnn NAPHTHAI Treatment Copper No. of Product per cent wt. per cent caustic alone. per cent wt. per cent caustic a1one per cent 10 wt.

. per cent wt. per cent wt. per cent 15 wt. per cent 15 Wt. per cent 15 Wt. per cent 15 wt. per cent 15 wt. per cent 15 wt. per cent 15 wt. per cent 15 wt. per cent 15 wt.

10 V01. per cent 15 wt.

. per cent 5 wt. per cent caustic alone .per cent 25 Wt. per cent caustic a10ne. :T TII: n per cent 40 wt. per cent caustic alone per cent 5 wt. per cent caustic+0.8 per cent ethylene oxide per cent 15 wt. per cent caustic+0.8 per cent ethylene oxide percent caustic+0.6 wt. per cent ethylene oxide per cent eaustic+0.2 wt. per cent propylene oxide. per cent caustic+0.4 wt. per cent propylene oxide. per cent caustic+0.6 wt. per cent propylene oxide. per cent caustic+0.2 wt. per cent isobutylene oxide per cent caustic-+0.4 wt. per cent isobutylene oxideper cent caustic+0.6 Wt. per cent isobutylene oxide... 5 Vol. per cent 15 wt. per cent caustic+0.2 wt. per cent ethylene oxide 5 Vol. per cent 15 wt. per cent caustic+0A wt. per cent ethylene oxide.

20 Vol. per cent 15 wt. per cent caustic+0.4 wt. per cent ethylene oxide- 20 Vol. per cent 15 wt. per cent caustic+0.4 wt. per cent ethylene oxide 20 Vol. per cent 15 wt. per cent caustic+0.6 wt. per cent ethylene oxide. 10 Vol. per cent 15 wt. per cent caustic-{-02 wt. per cent ethylene oxide (131 F.) 10 Vol. per cent 15 wt. per cent caustic+0.4 wt. per cent ethylene oxide (131 F.)... per cent caustic+0.6 wt. per cent ethylene oxide (131 F.)

3 Copper number of untreated stock==20, after initial caustic washing 16. Bromine number 65.5, sp. gray. 0.755.

It will be noted that in the presence of the alkylene oxide, a definite reduction in copper number was obtained which could not be realized when treating with the caustic solution alone.

The invention is broadly concerned with the use of alkylene oxides for the removal or conversion of mercaptan compounds from petroleum oils boiling below about 700 F. The invention is particularly concerned with the use of ethylene oxide in conjunction with an alkali hydroxide solution for the removal or conversion of mercaptan compounds from petroleum oils boiling in the motor fuel boiling range (80 F. to 430 F.).

Having described the invention it is claimed:

1. Process for the conversion of mercaptan compounds in a petroleum oil containing the same into relatively innocuous compounds which comprises contacting said petroleum oil with an alkylene oxide in the presence of an alkaline catalyst, said alkylene oxide being selected from the class of compounds represented by the structural formula Ra R:

wherein R, is selected from the class consisting of hydrogen and alkyl groups containing from 1 to 2 carbon atoms.

2. Process as defined by claim 1 wherein said petroleum oil boils in the range below about 700 F.

3. Process as defined by claim 1 wherein said petroleum oil comprises a motor fuel boiling in the range from about 80 F. to 450 F.

4. Process as defined by claim 1 wherein said alkylene oxide comprises ethylene oxide.

5. Process as defined by claim 1 wherein said alkylene oxide comprises propylene oxide.

6. Process as defined by claim 1 wherein said alkylene oxide comprises isobutylene oxide.

7. Process as defined by claim 1 wherein said alkaline catalyst comprises an alkali metal hydroxide solution containing from about 5 to 50% by weight of said alkali metal hydroxide.

8. Process as defined by claim 1 wherein the temperature used is below about 212 F.

.9. Process as defined by claim 1 wherein the concentration of the alkylene oxide used is in the range from about .05 to 5% by weight based upon the feed oil.

10. Process as defined by claim 1 wherein the concentration of the alkylene oxide used is in the range from about 0.2 to 0.8% by weight based upon the feed.

11. Process as defined by claim 1 wherein said alkaline catalyst comprises an alkali metal hydroxide solution containing from about 5 to 50 by weight of said alkali metal hydroxide and wherein the amount of said alkaline catalyst utilized is from about 1 to 20% by volume based upon the volume of petroleum oil being contacted.

12. Process for the removal of mercaptan compounds from an 011 containing the same which comprises contacting said oil in an initial stage with an alkali metal hydroxide solution, removing the treated oil and contacting the same in a secondary stage with ethylene oxide in the presence of an aqueous solution of an alkali metal hydroxide.

ERVING ARUNDALE. JOHN P. THORN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,261,866 Agruss et a1. Nov. 4, 1941 FOREIGN PATENTS Number Country Date 492,789 Great Britain Sept. 27, 1938 499,978 Great Britain Feb. 1, 1939

Claims (1)

1. PROCESS FOR THE CONVERSION OF MERCAPTAN COMPOUNDS IN A PETROLEUM OIL CONTAINING THE SAME INTO RELATIVELY INNOCUOUS COMPOUNDS WHICH COMPRISES CONTACTING SAID PETROLEUM OIL WITH AN ALKYLENE OXIDE IN THE PRESENCE OF AN ALKALINE CATALYST, SAID ALKYLENE OXIDE BEING SELECTED FROM THE CLASS OF COMPOUNDS REPRESENTED BY THE STRUCTURAL FORMULA

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